Diesel/Electric.

This is coolbert:

Thanks to the original comment and tip from Sven we have a listing of some of those very quiet diesel/electric submarines the capability of which is to remain undetected [?] from the most current American passive sonar systems. "Run Silent Run Deep" literally so!

1. German Type 212 class.

"The German Type 212 class . . . is a highly advanced design of non-nuclear submarine (U-boat). . .  It features diesel propulsion and an additional air-independent propulsion (AIP) system using Siemens proton exchange membrane (PEM) hydrogen fuel cells. The submarine can operate at high speed on diesel power or switch to the AIP system for silent slow cruising, staying submerged for up to three weeks without surfacing and with no exhaust heat. The system is also said to be vibration-free, extremely quiet and virtually undetectable."

2. Swedish Gotland class.

"The Gotland class submarines of the Swedish Navy are modern diesel-electric submarines . . . They are the first submarines in the world to feature a Stirling engine air-independent propulsion (AIP) system, which extends their underwater endurance from a few days to weeks."

"While submerged, the Kockums-built Stirling engine Air Independent Propulsion (AIP) system is used to drive a 75 kilowatts (101 shp) generator for either propulsion or charging the batteries."

3. French Scorpène class.

"The Scorpène class submarines are a class of diesel-electric attack submarine jointly developed by the French DCN and the Spanish company Navantia and now by DCNS. It features diesel propulsion and an additional air-independent propulsion (AIP)."

"The French MESMA (Module d'Energie Sous-Marine Autonome) system is being offered by the French shipyard DCN for the Scorpène class submarines. It is essentially a modified version of their nuclear propulsion system with heat being generated by ethanol and oxygen. A conventional steam turbine power plant powered by steam generated from the combustion of ethanol (grain alcohol) and stored oxygen at a pressure of 60 atmospheres."

4. Russian Lada class.

The Russian Navy's Project 677 Lada-class submarine (Russian: Лада) is a class designed by the Russian Rubin Design Bureau . . . [this is] A program to develop a 'fourth generation' diesel-electric submarine, it aimed to produce a highly improved version of the Project 636 Kilo class with much quieter, new combat systems, and possibly air-independent propulsion.

The Lada class similar to the nuclear Alfa class in that it primarily acts as a "test bed" for the latest and greatest technologies, diesel/electric of the quietest and most hard-to-detect variety.

AND LADA TO BE EXPORTED!

"Russia will sell four Lada class submarines to the PLA [Chinese communists] under the direct order of President Vladimir Putin, according to Moscow-based newspaper Kommersant on Dec. 20. 2012.."

The U.S. Navy currently has ZERO of the quiet diesel/electric boats and has NONE contemplated, that decision to go nuclear and stay nuclear having been made a long time ago!

coolbert.